Childhood acute lymphoblastic leukaemia (ALL)
What is childhood acute lymphoblastic leukaemia?
Acute lymphoblastic leukaemia (ALL) is a type of cancer that affects immature lymphocytes developing in the bone marrow. Under normal conditions these cells grow and mature into specialised white cells called B-lymphocytes (B-cells) and T-lymphocytes (T-cells). In ALL, they undergo a malignant (cancerous) change and multiply in an uncontrolled way, quickly crowding the bone marrow, and interfering with normal blood cell production.
Excess numbers of these abnormal lymphocytes, known as lymphoblasts, leukaemic blasts or leukaemic cells, spill out of the bone marrow and circulate around the body in your child’s blood stream.
Improvements in the diagnosis and treatment of children with ALL mean that, these days, almost all children treated for ALL will achieve a remission from their disease and most will be cured.
How common is ALL in children?
Each year in Australia around 180 children are diagnosed with ALL, making it the most common type of cancer overall in children aged 0 to 14 years.
Who gets childhood ALL?
The incidence of ALL is highest in children between the ages of two and four. It is more commonly diagnosed in boys.
What causes ALL in children?
No one knows exactly what causes ALL, but it is likely that there are a number of factors, rather than any single factor involved. Research is going on all the time into possible causes and a number of environmental factors continue to be investigated. To date however, none have been proven to cause ALL in children. There are certain factors that may put some children at a higher risk of genetic damage and therefore the development of ALL. These are called risk factors and include:
- infections - there is some evidence to suggest that viral infections may play a role in the development of ALL in some children. It is thought that delayed exposure to common childhood infections or an abnormal response by the child’s immune system to these infections may be involved. This is supported by the higher incidence of ALL reported in particular geographic or demographic areas. ALL is not contagious.
- ionising radiation - children exposed to large doses of ionising radiation (a type of energy emitted from x-rays and radioactive materials) before they were born or in the early years of life may be more at risk. It is unlikely that any children born in Australia are exposed to high enough levels of ionising radiation to cause childhood ALL.
- chemicals - exposure to high levels of benzene and other industrial solvents over a long period of time may increase the risk. Children in Australia are unlikely to be exposed to high enough levels of these chemicals to cause ALL.
- electro-magnetic radiation - in recent years there has been a great deal of controversy about the health effects of living very close to high-voltage power lines and other sources of electro-magnetic radiation such as mobile phones, mobile phone base towers and electrical equipment in our homes. The results of several large international studies have shown, however, that there is no clear evidence to support a link between childhood ALL and exposure to acceptable levels of electro-magnetic radiation in our environment.
- genetic factors - genetic factors may play a role in its development. Children with certain congenital disorders like Down syndrome and Fanconi anaemia are at an increased risk of developing ALL.
What are the symptoms of ALL in children?
Because ALL develops quickly, children are usually unwell for only a short period of time before they are diagnosed (days or weeks). The most common symptoms of ALL are caused by a shortage of normal blood cells in the circulating blood. These symptoms include:
- anaemia – a low haemoglobin level in the blood can cause symptoms including lack of energy; persistent tiredness and fatigue; pale complexion; weakness; dizziness; or unusually short of breath when physically active
- increased bleeding or bruising – a very low platelet count can cause bruising for no apparent reason, or excessive or prolonged bleeding following minor cuts or injury. Some children have frequent or severe nosebleeds or bleeding gums. Red or purple flat pinhead sized spots may appear on the skin, especially on the legs. These are called petechiae (“pe-teekee- a”) and are caused by tiny bleeds under the skin.
- frequent or repeated infections – with a low white blood count, children are more likely to develop frequent or repeated infections. These may present as minor skin infections, a sore throat, sore mouth, or slow healing of minor cuts and grazes. They may also develop chest infections (coughing), urinary tract infections (frequent passing of urine with a sensation of burning) and fevers. The leukaemia itself can cause a low grade fever in the absence of an infection.
- bone pain – bone and/or joint pain is common and results from the marrow being literally “stuffed” with leukaemic cells. Occasionally there may be deposits of leukemic cells in bone itself and this can cause localised pain.
- other symptoms – these may include swollen lymph nodes (glands), chest pain and abdominal discomfort due to a swollen spleen or liver.
Some of the symptoms described above may also be seen in other illnesses, including viral infections. Therefore, most children with these symptoms don’t have leukaemia. However, it is important to see your doctor if your child has any unusual symptoms, or symptoms that don’t go away so that they can be examined and treated properly.